Vacuum sealing structure



April 25, 1933- i w. K. RANKIN 1,905,751

vAcuuu smune STRUCTURE Filed Dec; 26, 1929 i T g 4/ 44 52 2 o 39 Z/ 29 10 28 $21 39 58 7 c I I P I 25 Hi8 Attorney.

Patented Apr. 25, 1933 UNITED STATES PATENT, ormca WILLIAM K. RANKIN, OI LANSDOWNE, PENNSYLVANIA, ASSIGNOB 'I'O em ELEC- TRIO COMPANY, A CORPORATION OF I03! vacuum smm'me srnucruaz Application Med December 28, 1929. Serial N0. 418,319.

My invention relates to vacuum sealing structure for leading-in conductors connected to electrical apparatus within an evacuated chamber.

An object of my invention is to provide an improved vacuum sealing structure which shall be simple and rugged in construction, of long life, and resistant to mechanical in- J fiy invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims 5 annexed to and forming a part of this specification.

Referring to the drawing, the single fig-ure thereof illustrates by way of example an elevational view of a vacuum switch, partly in section, embodying my invention.

Although obviously not limited thereto, my invention is illustrated as applied to a vacuum switch comprising a main evacuated chamber or casing 1, within which a movable contact 2 is adapted to engage a stationary contact surface 3 comprising the lower surface of a lead-in conductor stud 4. The movable contact may be operated in any suitable manner, and in the present instance is carried by a pivoted rod 5 extending through and hermetically sealed to a flexible diaphragm 6 sealed at its outer periphery by silver brazing and the clamping structure 7, to the container 1. Pivotal movement is imparted to the rod 5 through an operating member 8 controlled by suitable means (not shown). The contact 2 is electrically connected by a flexible conductor 9 to the terminal member 10 through the casing 1, which is of metal, as steel or copper. For the purpose of completely sealing the evacuated chamber after the air and gases have been evacuated through the exhaust conduit 11, a metallic cap 12 is seated within an annular recess 13 containing a molten low melting po1nt alloy 14, which is thereupon allowed to harden and complete the seal.

In order that the lead-in conductor stud .4 shall be suitably sealed with respect to the casing 1, it is necessary that the sealing leaks, suflicient to impairthe vacuum, may

be made without diificulty.

For the purpose of mounting the conductor stud 4 in order that shock or stress to the conductor shall be readily absorbed or compensated without causing injury to the bushmg or seal, the stud is provided with a collar or flange 15 which is welded thereto and which is secured to a plurality of spaced bolts 16 extending freely throu h the top end ca 17. The cap 17 is provi ed with a centra opening 17 through which the stud extends freely, and engages a gasket 18 at one end of a c lindrical' insulating bushing 19 provided at its lower end with a gasket 20 for engagement with the upper surface of a supporting and cooling structure 21. The stud 4 is screw-threaded, as at 22, adjacent its lower end and has fixed thereon a bearin plate 23 maintained in position by a pair 0 lock nuts 24 between which a shield 25 is supported. The bearing plate 23 freely abuts an insulating spacing collar 26 provided at its upper edge with a metal asket 27 and bearing against the lower side of the supporting plate 28, which is securedand sealed b a clamping structure 29 to the casing 1. or the purpose of protecting the insulating collar 26 from receiving a short circuiting metallic deposition, the shield 25 is cup-shaped and is spaced from and surrounds the outer side of the insulating collar. When the insulating collar 26 is unshielded, one cause of this short circuiting deposition is due to the high vacuum within the casing which causes free molecules at the surface of the metal walls of the casing to travel across the intervening space to the insulatin collar and .embed themselves in the insulation. After a comparatively short time, the insulating collar has a coating of metal due to this molecular de osition so that it is short circuited, with t e result that the conductor stud is in electrical contact with the casin The shield 25, however, being interpose in the path of these free molecules intercepts the same, and any other metallic particles, so that the insulating collar is kept free from a short-circuiting coating.

To the end that the stud 4 may be mounted for limited longitudinal movement with respect to the casing 1 and insulating bushing 19, the spaced rods 16, but one of which is illustrated, are each provided with a nut or stop member 30 between which and the upper surface of cap 17 resilient means, as a coil spring 31, is disposed. The stop nut 30 is ad usted so that the spring 31 is placed under initial tension, thereby urging the stud 4 upwardly so that the bearing plate 23 is firmly pressed into engagement with the spacing collar 26. It will accordingly be noted that shock is one direction and thermal expansion along the longitudinal axis of the stud 4 will be substantially absorbed and compensated by the springs 31 which are dis osed in a row concentrically of the stud 4.

or the purpose of providing a flexible insulatin seal for the conductor stud which shall li rewise safely withstand shock to the stud, there is provided a sleeve 32 of suitable insulating material, such as glass, at whose opposite ends are fused flexible diaphragms as the copper spinnings or punchings 33 and 34. The copper spinnings as illustrated, comprise annular corrugated members, the spinning 33 being fused at its inner edge to the upper end of the sleeve 32, and suitably sealed, as by a low melting point alloy 35 within an annular pocket to the outer edge of flange 36 which likewise is welded and sealed to the stud 4. The lower spinning 34 has its inner edge fused to the collar 32, and its outer edge sealed by a low melting point alloy 37 within an annular recess forming a part of the plate 28. It will be noted that the stud 4 is sealed with respect to the supporting plate 28, and that the conducting stud may partake of limited longitudinal movement by reason of the flexible spinnings 33 and 34 without impairing the seal.

Due to the fact that the conductor stud, when carrying comparatively large currents, must be provided with means for removing the heat generated, there is provided a cooling system comprising an intake conduit 38 in communication with an annular passage 39 formed within the supporting structure 21, and in communication with the interior of bushing 19 through the rows of apertures 40. The annular space 41 between the bushing 19 and the sleeve 32 communicates at its upper part with the interior of the stud 4 through the apertures 41, the stud being hollow and open only at its upper end. The interior of the stud 4 is provided with a guide tube 42 whose u per end is enlarged as at 43 to form a tight connection with the interior of the stud at a point above the apertures 41. The remainder of the tube 42 is spaced from the inner sides and lower part of the stud 4 so as to form an annular passage 44 in communication as its lower part with the interior of the hollow tube 42 which exhausts through the upper part of the stud 4 to atmosphere. Accordingly, a forced circulation of air or other suitable cooling medium may take PIMG in the direction indicated *by the arrows through the intake 38 and annular passage 39, apertures 40, upwardly within the annular space 41, through apertures 41' in the stud 4, downwardly within the annular space 44, to exhaust upwardly through the interior of the guide tube 42. It will therefore be noted that the cooling medium is passed interiorly of the stud 4 so as to effectively remove the heat as it is generated, thereby maintaining the conductor stud cool at all times.

When the conductor stud is to be used at lower current ca acities so that a forced circulation of air or cooling is not necessary, a system employing natural convection currents within the conductor stud may be used. Such a system is disclosed and claimed in a copending application Serial No. 426,677, filed February 7, 1930 by A. M. Poniatofi'.

During the baking or degasifying process in the construction of the vacuum apparatus, during which occluded gases are removed from the switch parts, the guide tube 42 may be removed from the interior of the stud and a heating unit, as a resistance unit, inserted therein to apply heat to the stud.

It shall be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is 1. In vacuum apparatus comprising an evacuated casing and a substantially rigid electrical conductor extending therein, a mounting for positioning said conductor with respect to said casing for limited longitudinal movement in one direction, and a flexible diaphragm independent of said mounting for sealing said conductor with respect to said casing.

2. In vacuum apparatus comprising an evacuated chamber, the combination of an electrical conductor extending within said chamber, an insulating flexible seal comprising a sleeve of insulating material within which the conductor is disposed, and a flexible metallic diaphragm annular in form sealed to each end of said sleeve, one of said diaphragms beingsealed at its outer eriphery to the conductor and the other diap ragm being sealed likewise at its outer periphery to said chamber, and insulating means independent of said seal mounting said conductor for limited longitudinal movement in one direction with respect to said chamber.

3. In vacuum apparatus comprising an evacuated chamber, the combination of a conductor stud extending within said chamber, a flexible diaphragm for sealing said stud with respect to said chamber, resiliently biased means for urging said stud in a longitudinal direction, and an insulating member preventing longitudinal movement of said stud in said biased direction thereby serving to position said stud.

4. Vacuum apparatus comprising an evacuated chamber, an electrical conductor extending throu h a wall of said chamber, means for flexibly sealing said conductor with respect to said chamber, and means for resiliently mounting the conductor for limited movement in one direction with respect to said wall comprising a flange forming part of said conductor, structure fixed with respect to said wall, and resilient means coacting with said structure and flange to resiliently bias the conductor into position with respect to said wall.

5. Vacuum apparatus comprisin an evacuated chamber, an electrical con uctor extending through a wall of said chamber, meansfor sealing said conductor with respect to said wall, and means for resiliently, mounting said conductor for limited movement in one direction with respect to said wall comprising an insulating bushing within which the conductor is disposed, said bushing having an end cap at its outer end, resilient means coacting with said end cap and conductor for biasing the conductor longitudinally of said bushing, and an insulating spacing member coacting with said wall and conductor for positioning the conductor against the bias of said resilient means.

6. Vacuum apparatus comprising an evacuated chamber, an electrical conductor extending through a wall of said chamber, said conductor being hollow and open at its outer end, means for sealing said conductor with respect to said wall, and a cooling system for removing heat from the interior of said conductor comprising aperatures ex tending through the sides of the conductor exteriorly of said sealing means, and a tubular guide member disposed within the conductor for permitting circulation of a cooling medium through said apertures and longitudinally in one direction through the interior of the conductor and in the opposite direction through said tubular member to exhaust through the outer open end of the conductor.

7. Vacuum apparatus comprisin an evacuated chamber, an electrical con uctor extendin through a wall of said chamber, said con uctor being hollow and open at its outer end, means for sealin said conductor with respect to said wal an insulating mounting for the conductor within which the conductor and sealing means are disposed, and a cooling system for removing heat from the conductor comprising an annular passage between the sealing means I and insulating mounting, said annular passage adapted to be in communication with a source of supply of cooling medium, apertures extending through the conductor exteriorly of the seal for permitting communication between said annular passage and the interior of the conductor, and a tubular guide member disposed within and centrally of the conductor for permit-ting circulation of a cooling fluid from said annular passage in one direction through the interior of the conductor and in the opposite direction centrally thereof through the tubular member and outer end of the conductor to exhaust.

8. In vacuum apparatus comprising an evacuated chamber and an electrical conductor stud extendin through a wall of said chamber, means or mounting and sealing said stud comprising an insulating sleeve within which said stud is disposed, said sleeve being sealed at its op osite ends to said wall and stud respective an insulating bushing spaced from and enclosin the insulating sleeve, an end cap for said bushing through which the conductor stud extends, spring means coacting with said end cap and stud for biasing the stud in a longitudinal direction, and an insulating spacing collar for limiting longitudinal movement of said stud in its biased direction and maintaining said spring means under tension.

9. he combination with a vacuum switch comprising an evacuated casing and relatively movable contacts disposed therein, of means for mounting and sealing a rigid conductor forming one of said contacts comprising a diaphragm for flexibly sealing said conductor with respect to said casing, and means independent of said sealing means for insulating and mounting said conductor whereby thermal expansion lon itudinally of the axis of said conductor may compensated.

In witness whereof, I have hereunto set my hand this 23d day of December 1929.

WILLIAM K. RANKIN. 

